Metastatic Lesion From Clear-cell Renal Carcinoma After 40 Years and a Review of the Literature

Solitary Masseter Metastasis from Renal Cell Carcinoma: A Rare Case Report

Background

Renal cell carcinoma (RCC) frequently presents with metastatic spread, sometimes many years after treatment. However, masseter muscle metastasis is extremely rare, with just six reported cases in literature, and none in the United Kingdom (UK). Given its rarity, we hope our case will add to the body of knowledge on the subject and encourage clinicians to maintain a high index of suspicion when reviewing patients with previous RCC and an unexplained mass.

Case Summary

Here presented is a 62-year-old man who previously underwent left radical nephrectomy in 2014 for an 11 cm clear cell renal carcinoma (ccRCC). He had subsequent right adrenalectomy in 2020 for a 19 mm recurrence, which was excised with clear margins. He then presented in 2022 with a three-month history of enlarging painless mass in the left side of his face. Imaging was inconclusive, but biopsy showed a singular ccRCC metastatic deposit in the masseter. Surgical resection was not possible due to extension into the infratemporal fossa, and he was referred for radiotherapy.

Conclusions

Masseter muscle, whilst rare, can be a site of distant metastases for renal cell carcinoma. Diagnosis relies on a high index of clinical suspicion in patients with prior RCC, combined with cross-sectional imaging and biopsy. Early detection gives the best chance for cure with metastasectomy.

Masseter Muscle Metastasis of Renal Cell Carcinoma: A Case Report and Literature Review

Background

Patients with renal cell carcinoma are often troubled by metastases, but masseter muscle metastases are particularly rare.

Case Presentation

We reported a 76-year-old male who did not show any recurrence and metastasis after the nephrectomy until 5 years later. The metastatic mass was found with the protrusion of masseter muscle area. Computed tomography and ultrasonography indicated a hypervascular mass, and pathology confirmed the masseter muscle metastasis of renal cell carcinoma. Complete metastasectomy was performed with the preserval of facial function and appearance. No local recurrence or distant metastasis was found in follow-up.

Conclusion

Our report indicates masseter muscle can be a metastatic site of renal cell carcinoma, regardless of its rarity. Long-term comprehensive surveillance is needed for patients with renal cell carcinoma. Muscle metastases can disguise as benign mass, while multiple imaging and pathology are important in identifying their sources. If possible, complete metastasectomy with function retention is recommended for masseter muscle metastases.